1. Field of the Invention
The present invention relates to a Fresnel optical element such as a Fresnel lens or Fresnel mirror and an optical system using the Fresnel optical element.
2. Description of the Related Art
A Fresnel optical element serving as a screen that receives irradiation of light beam from a projector for projection of an image near the Fresnel surface and effectively reflects the light beam toward an observer is disclosed in Japanese Patent No. 4,128,599 or Japanese Patent No. 4,149,493. Further, a linear Fresnel mirror with its reflection surface having no power that reflects a projection image almost equivalent to an image obtained when a plane mirror is tilted is disclosed in JP-H03-209403.